Manufacture of brake lining



Patented Oct. 31, 1933 UNITED STATES PATENT OFFICE MANUFACTURE or BRAKEmore corporation of Illinois No Drawing. Application December 7, 1928Serial No. 324,572

14 Claims. (Cl. 188-251) This invention relates to friction materialssuch as brake linings, clutch facings, etc., and has for its object toprovide a material which will not injure the brake drum, which has acoefllcient of friction which is as constant as possible, and which isnot injured by heat. I have found that these and other advantages can beattained by introducing into the friction material certain salts orother non-metallic substances having desirable effects set forth below.

Preferably these substances are relatively inert at ordinary brakingtemperatures, except for their mechanical effect as a part of thefriction mass, but at relatively high temperatures such as might causescoring,-i. e. ordinarily between 1,000 F. and 1,700 F.,--they soften ormelt or are otherwise activated to minimize the frictional efiect of thelining, probably by lubricating the surface which engages the brakedrum. Many substances of high melting point have this desirablecharacteristic, among them being sodium chloride, sodium cyanide orferrocyanide, barium carbonate alone or mixed with sodium cyanide,bichromate of potassium, and others. These materials lower thecoeificient of friction, thereby minimizing the tendency to grab, and atthe same time make the coefficient of friction more uniform undervarying temperatures, pressures, and other conditions. Moreover, thecoefficient drops somewhat as the salt softens or melts, thus softeningthe final retarding effect.

Itwill be seen that among these are a. number of salts, including thesodium cyanide and ferrocyanide, the barium carbonate, and thebichromates, which have a case-hardening effect on steels. This,according to a highly important phase of my invention, permits the usein the brake of a relatively low-carbon drum, which is easily worked andtherefore inexpensive, without scoring and without flaking off particlesof steel to become imbedded in the brake lining. The carbon-containingsalts, preferably sodium cyanide, while relatively inert during ordinarybraking, are activated by excessive surface temperatures of the steel,and also of the lining, to react on the steel drum to introduce carboninto its surface to case-harden it. The tendency of the drum surface tosoften at these high temperatures facilitates the case-hardening effect.

Similarly the chromium-containing salts harden the drum gradually in useby introducing chromium into the surface of the steel when activated bythese high temperatures.

Some of these materials, notably the sodium cyanide, also have theadvantage that the cyanide,

for example, forms fumes at high temperatures which act on the copper ofthe brass wire used in the asbestos yarn from which the usual lining iswoven, and on the copper of the brass lining rivets, to form a'softcompound which wears away without scoring the drum, merely forming abrown powder whlchsifts out of therdrum as fast as it is formed.

A woven lining of my new type may be formed by impregnating the yarnforming the transverse threads of the lining, and which ordinarilyconsist of an asbestos-copper or asbestos-brass yarn,

with a suitable friction agent mixed with powdered sodium cyanide. Suchan agent may consist of a mixture including an oxidizing oil such as 7 0China-wood oil or a mixture of China-wood oil and castor oil. diluted ifdesired with kerosene and/or gasoline, or in some cases a vulcanizablerubber composition is used. The yarn forming the warp, or longitudinalthreads, is impregl6 nated with this or a similar agent just before itreaches the loom where it is woven, and may be dusted with pulverizedsodium cyanide or other salt while still wet and before weaving on theloom. The fabric after weaving is cured in the usual manner by heatingand rolling.

If preferred, the lining may first be woven, then impregnated with asolution of the salt, then dried, and finally impregnated with the usualwaterproof bituminous friction dope. Where asbestos is formed into apaper made from a pulp, and thereafter made into the lining, the saltmay be mixed into the pulp.

A molded lining may be made by impregnating asbestos fiber with phenolicor other synthetic 9 condensation material such-as furfural containingthe sodium cyanide or other salt. This material may also be used with awoven lining in place of the materials described above. The impregnatedfiber is molded under heat and pressure.

Asbestos fiber or sheets may also be impregnated with a sodium cyanideor other salt solution and thereafter treated with synthetic resin orrubber for water proofing purpose previous to curing or molding underheat or pressure and heat. In still other methods of manufacturinglining, it may be desirable to mix the salt directly into the usualfriction dope withwhich the fabric is impregnated.

In addition to the drum-hardening effect, and the minimizing of scoringand grabbing, I find that these salts, notably sodium chloride andsodium cyanide, give desirable and hitherto difflcul y-obtainablefriction characteristics to the 0 lining regarded purely as a frictionmaterial. Thus tests show that the coefficient of friction is much morenearly constant than usual, but drops away slightly at high pressure,probably due to liquidation of the salt, thus giving an additionalsafeguard against grabbing. The average wear in severe use andespecially at high temperatures is more than doubled, probably due to aglaze of the salt forming on the surface of the lining.

It is not my intention to limit the invention to the exact materials, orto the exact methods described above, or otherwise than by the terms ofthe appended claims. Part of the subjectmatter of this case is continuedfrom my prior application No. 319,459, filed November 14, 1928.

I claim:

1. A friction material for a brake lining comprising a substantialamount of barium carbonate.

2. A friction material for a brake lining comprising a substantialamount of barium carbonate and sodium cyanide.

3. A friction material for use in rubbing engagement with steel, andwhich comprises a carbon-containing salt activated by relatively hightemperatures to carburize the surface of the steel.

4. A friction material, for a brake lining or the like, containing acyanide.

5. A friction material, for a brake lining or the like, containing analkaline cyanide.

6. A friction material, for a brake lining or the like, containingsodium cyanide.

7. Brake lining friction material comprising a woven body with itsthreads carrying a cyanide.

8. A brake lining comprising asbestos and a metal, together withimpregnating material containing a cyanide.

9. A brake lining material impregnated with a drying oil containing acyanide.

10. A brake comprising a steel drum, in combination with frictionmaterial engaging the drum and containing a cyanide.

11. That method of making a brake lining which comprises mixing anasbestos material with a cyanide.

12. That method of making a brake lining which comprises forming a yarn,impregnating the yarn with a friction agent and a cyanide, andthereafter weaving the yarn into a brake lining fabric.

13. That method of making a brake lining which comprises impregnating anasbestos material with a cyanide and waterproofing agent.

14. That method of making a brake lining which comprises impregnating anasbestos material with a cyanide and synthetic resin and thereaftermolding it under heat or pressure and heat.

ADOLPH ROSNER.

